If you're talking about Frank boning the blond daughter of his girlfriend. I don't necessarily think Frank had any say in the matter. He ate about ten oxy's and the dude is always drunk. From the scene it didn't even look as if he were participating.

That being said, you're right - he's in a heap of trouble!

Yeah, I don't think it was a decision Frank made. Hated to see that happen, too.